Exposure measurement at dawn/dusk

[Ron Marshall]

Attached is the spreadsheet without the formulas showing, for clarity.

[Ron Marshall]

The last post was not very clear so here is the table broken in two parts.

[Gregory Gomez]

Ron,

Outstanding!

I have three questions:

1) In reciprocity departure with color film, shouldn't one also use color correction filters to adjust for the inevitable color shift?

2) Would one have to include a filter factor if color correction filters were used?

3) Would E6 processing need to be adjusted for the very long exposures of the slide film?

Just curious.

[MJSfoto1956]

and while we are on the subject, how about doing the spreadsheet for light DIMINISHING during the exposure??

[Ron Marshall]

Gregory,

First let me say not so outstanding. Right after posting it I noticed that I had overlooked a couple of things that will change the results somewhat. But for rates of change around 0.1 - 0.2 stops per minute the spreadsheet will give fairly good values.

I'll post the corrections soon.

Yes CC filters should be used. Fuji lists the correct filtration for a given time.

I have never used CC filters as I shoot mostly B/W, but the same principles apply, the metered time would be corrected using the filter factor before entering it in the spreadsheet.

For exposures up to 8 minutes there is no need to modify development as long as a reciprocity failure correction has been applied. For times beyond that I have no idea.